Power hammer

ABSTRACT

In a hydraulic hammer mechanism, the hammer weight is reciprocated through its working and return strokes by a ram cylinder circuit, the latter being controlled for automatic or manual operation by a hydraulic control circuit. In either automatic or manual position, the length of stroke, speed, power and balance of the ram cylinder may be independently regulated. Moreover the ram cylinder is self-regulating with the necessary built-in safety features to avoid shock or damage to the mechanism or circuitry. Still further, the ram cylinder may be actuated through a power or gravity stroke as desired, and is characterized in that considerably more power and acceleration can be developed in the ram cylinder through each working and return stroke while isolating the cylinder circuit from the hydraulic control circuit.

United States Patent [72] Inventors Kenneth H. Hoen Littleton;

Walter J. Chapman, Denver; Robert W. Jones, Englewood, C010.

[2]] Appl. No. 810,857 [22] Filed Aug. 5,

Division of Ser. No. 411,978, Nov. 18, 1964, Patent No. 3,408,897 [45] Patented Mar. 9, 1971 [73] Assignee Champion Manufacturing, Inc.

Denver, Colo.

[54] POWER HAMMER 12 Claims, 7 Drawing Figs.

52 u.s.c| 91/26, 91/277,91/396,9l/405,9l/436,92/l6l,

51 lnt.Cl ..Fl5b 15/22, F0l3l/00 so FieldolSearch 9l/26,405

(Cursory), 277; 299/32, 33 (Cursory), 37; 173/27 [56] References Cited UNITED STATES PATENTS 2,672,331 3/1954 Cornett 173/27 3,082,746 3/1963 Kerridge 91/26 3,303,746 2/1967 Schmoeger 9l/26 Primary Examiner-Paul E. Maslousky AttorneyJohn E. Reilly ABSTRACT: In a hydraulic hammer mechanism, the hammer weight is reciprocated through its working and return strokes by a ram cylinder circuit, the latter being controlled for automatic or manual operation by a hydraulic control circuit. In either automatic or manual position, the length of stroke, speed, power and balance of the ram cylinder may be independently regulated. Moreover the ram cylinder is self-regulating with the necessary built-in safety features to avoid shock or damage to the mechanism or circuitry. Still further, the ram cylinder may be actuated through a power or gravity stroke as desired, and is characterized in that considerably more power and acceleration can be developed in the ram cylinder through each working and return stroke while isolating the cylinder circuit from the hydraulic control circuit.

' Patented March 9, 1971 4 Sheets-Sheet 1 illlll 25 I "mm-n I luv IN VENTOR. H.

KENNETH WALTER ROBERT Patented March 9, 1971 4 Sheets-Shem. 4.

wmm

INVENTOR. H. HOEN KENNETH WALTER J CHAPMAN ROBERT W, JONES BY a.

Q I ff ATTNEY POWER HAMMER This is a division of application Ser. No. 41 1,978, filed Nov. 18, 1964, now U.S. Pat. No. 3,408,897.

This invention relates to fluid actuated power hammers, and more particularly relates to a vehicle-mounted hammer mechanism and a hydraulic control circuit therefor being adaptable for use in cutting, scoring or breaking concrete, tamping earth fills and in other related earth-working operations.

Mobile hammer units are conventionally designed to suspend an impact tool or other working implement at the lower end of a ram or other heavy 'mass which is guided for reciprocal movement alternately to perform a working, or down, stroke and a return, or lift, stroke. Customarily, the hammer mechanism is mounted on a vehicle which can be advanced to the work site and be maneuvered into position for performing work; and a preferred manner of mounting the hammer mechanism and impact tool on a vehicle and for con trolling the movement and disposition of the tool in relation to the work is set forth and described in detail in our copending application for United States Letters Patent entitled MOBILE HAMMER UNIT AND POSITION CONTROL AP PARATUS THEREFOR, Ser. No. 411,979, filed Nov. 18, 1964, now U.S. Pat. No. 3,333,646. Also, as set forth and described in copending application for patent entitled HAMMER TOOL ATTACHMENT AND TOOL, Ser. No. 345,006, filed Feb. 14, 1964, now U.S. Pat. No. 3,318,392, and assigned to the assignee of this invention, various different tools may be attached to the lower end of the ram or hammer head to perform a number of different operations, and accordingly the power requirements for the ram and tool will vary over a wide range depending upon the nature of work and type of tool carried by the ram. Usually, the ram is either of the gravity drop or power driven type and, in accordance with the present invention, the control circuit for the ram and tool enables operation either as a gravity drop or power hammer.

in the present invention, the ram is driven or powered by means of a fluid actuated motor, preferably in the form of a hydraulically operated power cylinder and piston, with the ram and tool supported for movement in response to reciprocation of the piston within the cylinder. In driving the tool through its working stoke, it is highlydesirable that the fluid control circuit and power cylinder be so designed that the tool can be rapidly accelerated over a relatively short distance of travel to attain maximum velocity and force at impact; and in order to permit development of the highest possible impact forces, the external effect of the resultant shock or reaction at impact upon the hammer mechanism should be effectively absorbed by the vehicle and supporting assembly, and the internal effect on the fluid system should be isolated as much as possible from the control circuit and fluid source. Moreover, on the return stroke it is advantageous initially to effect rapid acceleration under an additional force in order to free the tool in the event it should become lodged or stuck in the working surface. It is important also that the power cylinder be selfregulating in order to rapidly decelerate in the event it reaches the end limit of its travel in either direction, since this will enable the operator safely to impart the maximum number of blows over a given period of time.

Accordingly, a principal object of the present invention is to provide a power system for a mobile hammer unit in which the working or impact tool is operated rapidly and with a high degree of force through its entire stroke without requiring a correspondingly high power source.

Another object of the present invention is to provide a hydraulically actuated hammer mechanism in which operation of an impact tool through its working andreturn stroke is effectively accomplished by interrelated but separate hydraulic control means, the operation of which is fully coordinated through each cycle.

It is a still further object to provide a hydraulically actuated hammer unit in which operation of the hammer tool through its working stroke is effectively isolated from the fluid source, and with provision being made for relieving the hydraulic pressure in response to excessive loads imposed on individual parts of the system so as to avoid damaging the hammer mechanism.

A further object of the present invention is to provide an automatic pilot control circuit which, according to the direction of fluid flow to and from the power hammer, will automatically control reversing of the hammer in either direction of travel and in such a way as to greatly minimize shock on the system between strokes.

Other objects and advantages of the present invention will become more apparent from a consideration of the following detailed description and claims, taken together with the accompanying drawings, in which:

FIG. 1 is a front'elevational view of a preferred form of power hammer mechanism disposed for sliding movement along a hammer guide frame assembly.

FIG. 2 is a sectional view, taken about lines 2-2 of FIG. 1.

FIG. 3 is a top plan view of the preferred form of power hammer mechanism.

FIGS. 4 and 4A are enlarged fragmentary views partially in section of the power cylinder assembly for the power hammer mechanism, in accordance with the present invention.

FIGS. 5 and 6 are diagrammatic views, with portions thereof enlarged and represented in cutaway form of a remote control valve circuit and ram cylinder control circuit, respectively, for the hydraulic control circuit, in accordance with the present invention.

Referring in detail to the drawings, there is illustrated in FIGS. 1 to 3 a hammer mechanism being broadly comprised of a hammer weight or ram 10 with an impact tool 11 suspended at its lower end, and the ram being mounted for reciprocal sliding movement along a hammer guide frame assembly 12. The detailed construction and arrangement of the hammer weight in relation to the guide frame assembly is set forth in said U.S. Pat. No. 3,333,646; and, as a setting for the present invention, generally the hammer weight 10 is of hollow heavywalled construction with opposite elongated sides 14 slidable along the inner surfaces of a pair of vertically extending tubular track members 15, the latter being interconnected to form a rigid tower structure by means of a lower offset cross brace 16 and an upper cross brace member 18. Height adjustment of the tower structure including the hammer head and tool relative to the ground surface is suitably accomplished by slidably disposing the outer surfaces of the tubular track members in a pair of spaced outer vertical guideways 20 forming divergent extensions of a main support or frame 22 for the entire guide frame assembly; and to control height adjustment of the tower, a pair of lift cylinders 24 are positioned just rearwardly and to one side of each of the track members for connection between the stationary frame portion 22 and brackets 26 on the lower cross brace 16 of the tower structure. Although not shown in FIGS. 1 to 3 herein, the entire hammer guide frame assembly is mounted in swiveled relation to one end of an overhead boom assembly carried by a tractor vehicle so that the guide frame assembly will follow movement of the tractor and boom assembly, as well as being independently movable in relation to the boom assembly, to position the tool in desired relation to the work.

Considering in more detail the construction of the hammer mechanism, the ram 10 has a lower hollow extension 30 of reduced size which terminates in a closed lower end 32 having an adapter 33 for attachment of the hammer tool 11, or other suitable tools or implements utilized in earth working operations. The closed lower end 32 also includes a pair of spaced upwardly directed bracket plates 34 adapted to receive a pin 35 having a generally spherical bearing 36 thereon to establish swiveled connection of the ram and attached tool with a ram cylinder assembly T. Essentially, the assembly T includes a power cylinder 40 depending downwardly from the top of the tower structure and terminating in a reinforcing sleeve structure 42, and a piston rod 43 projecting downwardlythrough the sleeve structure 42 to terminate in a yoke 44 formed for insertion of the ball-type bearing 36 therein. In a manner to be described, the ram cylinder assembly T also has its upper end supported in swiveled relation by ball joint assembly 45 within the cross head or main brace 18 at the top of the tower structure, thereby suspending and guiding the ram and attached tool 11 from the tower structure for reciprocal sliding movement along the track member 15. Thus, by selectively applying fluid under pressure to opposite ends of the power cylinder 40, in a novel manner to be described, the ram and attached tool are alternately driven through a working and return stroke to impart a series of blows to the surface being worked.

In the preferred form, fluid is supplied to the ram cylinder assembly T through a manifold block 47 mounted on the tower structure across the upper ends of the track members and main brace 18. The ram control members are represented in FIG. 6, but their structural mounting in relation to the ram cylinder assembly is not shown in FIGS. 1 to 3 since this relation, as such, forms no part of the present invention. However, for the purpose of compact design, the ram accumulator and over travel accumulator P are positioned within the hollow trace members 15; and the check valves B and C, flow sensor assembly D and pressure booster N preferably are attached to the manifold block and are in direct communication with the manifold to control flow of fluid from the main system into the ram cylinder. Above the ram cylinder, a main pressure line 48 is shown leading from the manifold 47 to a cylinder head 50 in order to supply fluid to the upper end of the chamber formed within the power cylinder; and a feed tube 52 is shown alongside the power cylinder 40 to serve as a means of fluid connection between the manifold and the lower end of the cylinder.

RAM CYLINDER ASSEMBLY Referring to FIGS. 3, 4 and 4A, the ball joint assembly 45 includes a housing 54 which is attached to the cross brace 18 by suitable bolts 55 and is provided with an inner bearing 56 which engages a generally spherical bearing 58 secured to the upper end of the power cylinder 40. The bearing 58 is locked in place between a lower thrust nut 59 and lower threaded end 60 of the cylinder head 50. The cylinder head has a central bore 61, and a pressure line 48 leads into one side of the head for communication through the bore 61 with the upper end of the cylinder. As best seen from FIG. 3, a backup plug 62 is inserted radially through the body of the cylinder head at an angle to the pressure line 48 and has a rod 63 projecting outwardly into engagement with the side of the cross brace 18. Here, the backup plug is positioned to compensate for side loads imposed on the ram cylinder under introduction of hydraulic fluid under pressure both through the pressure line 48 and feed tube 52 to the upper and lower ends of the cylinder 40. The housing 54 is provided also with a vertical through-bore 65 to receive the upper end of a rocker arm shaft, see FIG. 2, for a stroke limit cylinder assembly U to be hereinafter described in more detail.

In order to conduct fluid to and from the lower end of the power cylinder 40, the feed tube 52 extends downwardly in spaced parallel relation along one side of the cylinder and communicates with a generally L-shaped bore 68, at the upper end of the sleeve 42, which converges laterally into an inlet port 69 formed in the wall of the cylinder in spaced relation above the lower end. In addition, a vertical bore 70 extends from the bore 68 downwardly through the body of the reinforcing sleeve for communication through lateral bore 71 and inlet port 72 with the bottom extremity of the cylinder. A check valve 73 is positioned to control introduction of fluid from the bore 70 lateral bore 71 into the cylinder, and suitably includes a downwardly facing check valve seat 74 and a ball 75 biased upwardly by means of spring 76 into normally closed relation against the seat. An error relief valve assembly 78 projects laterally through the wall of the reinforcing sleeve and across the bore 70 into communication with a vertical channel 79 formed between the inner surface of the sleeve and outer wall of the cylinder, and which channel communicates with the lateral port 71 inwardly of the check valve for a purpose to be described. The error relief valve includes a valve seat 80 and valve 81 biased against the seat by spring 82 so that at a selected or predetermined pressure level, the valve will open to permit fluid flow outwardly from the channel into the bore 70.

A piston 85 of elongated cylindrical configuration is mounted at the upper end of the piston rod 36 and is sized for disposition in close-fitting relation within the power cylinder alternately to impart a downstroke and lift stroke to the ram and impact tool. It will be noted that the piston has a series of axially spaced peripheral grooves 86 on its external surface and the spacing between grooves is progressively reduced from the lower to the upper end of the piston. In addition, the lower extremity of the piston rod has a grooved striker bushing 87, and the uppermost series of peripheral grooves 86 are each provided with a ring seal arrangement, represented at 90, in order to establishsealed relation between the piston and the cylinder wall. In this way, on each downstroke the piston will initially displace fluid. ahead of its through the port 69, but toward the end limit of travel on each downstroke the striker bushing 87 and piston in passing over the entrance to the port 68 will tend to entrap the remaining fluid between the end of the bushing and lower end of the cylinder; and, in the absence of a seal between the end surface and the port 69, will force the fluid to gradually leak back past the end surface of the piston through the spaced annular grooves into the port 69 and into the channel 79 thus causing rapid deceleration at the end of its travel.

In order to minimize hydraulic shock on the system, uniform deceleration of the piston is achieved in a unique way from a maximum velocity, as the piston crosses the port 69, to a complete stop at the lower end limit of travel, this being accomplished by maintaining a constant pressure condition across the lower end surface of the piston once it passes the port 69. To maintain a constant pressure, the grooves 86 are formed at predetermined spaced intervals along the external piston surface, each groove having the effect of increasing resistance to movement of fluid to the port 69, so that as the number of grooves between the lower end of the piston and port 69 increases the resistance to displacement of fluid into port 69 will correspondingly increase as piston speed is rapidly slowed toward the end of its stroke. Thus, the grooves are so spaced as to prevent reduction in pressure due to reduced speed of travel; and since there is a progressive reduction in velocity or speed of the piston the number of grooves between the port 69 and lower piston end must be progressively increased, or in other words, the spacing between grooves is progressively reduced in direct relation to the rate of reduction in speed or velocity.

In the event that the fluid pressure level increases beyond the constant predetermined level, the relief valve 78 is set to open at the predetermined level to permit fluid to escape through the bore 70 into port 68. Accordingly, under uniformly decelerated motion as described, destructive hydraulic shock to the system is greatly minimized thereby minimizing the dwell time necessary between strokes and permitting a substantial increase in stroke speed without damaging the system. y

The reinforcing sleeve 42 has a lower end 92 forming an extension of the lower end of the cylinder 40 with an upwardly facing striker bushing 93, backed by a seal assembly 94 including a compression spring 95, to establish sealed engagement with the lower end of the piston at its lower end limit of travel on the downstroke. On the lift or return stroke, fluid applied under pressure through the feed tube 52 will enter the port 72 and a shallow recessed area 72' surrounding the striker bushing 87 to cause initial displacement of the piston away from the striker bushing 93; then as the piston rod is forced upwardly past the port 69, fluid passes through the port 69 behind the piston to complete the lift stroke. Again referring to FIG. 4, the bore 61 in cylinder head 50 is reduced in size and the top of the piston 85 is provided with a correspondingly reduced portion 96 with spaced annular grooves 97, the

reduced end portion being dimensioned for movement into close-fitting relation through the bore 61. Thus, on the lift stroke, fluid is displaced ahead of the upper end of the piston through the pressure line 48 into the manifold 47, and should the piston reach its upper extreme end limit of travel, the reduced end portion 96 will move through the bore 61 thereby constraining a portion of the fluid between the upper end of the piston and the upper end wall of the cylinder head adjacent to the bore till and forcing the fluid to leak under the increased resistance of the grooves between the reduced end portion and wall of the bore 54 into the pressure line. Again the spacing between grooves is such that the piston is rapidly but uniformly decelerated to a complete stop at the end of its stroke.

HYDRAULIC CONTROL GIRCUlT Selective control of the operation of the ram cylinder assembly is obtained by means of a novel hydraulic control circuit shown in FIGS. 5 and 6. FIG. 5 illustrates the system supply and remote control valves accessible to the operator, and FIG. 6 illustrates the ram cylinder assembly T and associated cylinder controls on the manifold 47 which, in cooperation with the remote control valves, will determine the power, speed, direction and length of stroke of the ram and impact tool. Referring generally to H6. 5, a primary source of hydraulic fluid under pressure is represented as consisting of a main reservoir run leading through a constant pressure tank 101 to a pressure-compensated variable volume pump S; and a suitable system return including an oil cooler is designated at 102. For purposes of illustration, the pump S may be of relatively large capacity and capable of supplying fluid at the desired volume and pressure, for instance on the order of 2200 pounds per square inch, and likewise at the desired high rate of flow, for example, on the order of gallons per minute and may be controlled for on-off operation by a threeway valve represented at X, the latter having a pump shutoff line N33 to the pump and another fluid line EM into the control circuit for porting fluid out of the system when the pump is not in operation. The pump operates to supply fluid under pressure through main supply line 105, and from this supply line 3105 a branch line we leads to system accumulator V, branch line W7 leads through power limit valve W, and branch line llllh leads through flow control valve A. Briefly, the valve A may be described as the central control valve for the entire circuit as it controls the direction of fluid flow to the cylinder in order to drive the ram piston 35 through each stroke. At one end of the control valve A is a selector valve K which, under the direct control of the operator, will set the ram cylinder either for power down" or gravity down" movement. Also, under the control of the operator, an automatic-manual selector valve J will, when shifted to the automatic position, cause the ram to operate continuously through the desired number of cycles; or when shifted to a manual position permit the operator to control movement of the ram throughout each stroke by means of a manual stroke control valve 1. in either the manual or automatic position, the operator may control stroke length by means of the control valve E, control downstroke power by regulating the limit valve W, and control return or lift stroke speed by regulating valve H. Referring to FIG. 6, the ram cylinder assembly is represented at T, and the piston $5 is powered through its downstroke or working stroke by an energy storing device defined here by ram accumulator O, which selectively applies fluid pressure, under the control of pilot check valve B, to the line 49% into the cylinder head 50. The ram accumulator Q is charged by the system accumulator V, shown in FIG. 5, through line 107 from the power limit valve W. Here, a pressure differential is established between the system accumulator V and the ram accumulator Q such that when the power limit valve W opensthe line W7, fluid flows under pressure from the system accumulator to charge the ram accumulator for the power down stroke. To supplement the fluid under pressure supplied from the ram accumulator 0 during the downstroke, fluid displaced by the piston through the lower end of the cylinder is returned, by way of the feed tube 52 through a fluid displacement circuit defined by line M4 to pressure booster N, line to flow sensor D to line 1116 and through pilot check valve C to line 118 into the pressure line $8 at the upper end of the cylinder. Therefore, assuming that both pilot check valve B from the ram accumulator and pilot check valve C are both open, pressure is applied to the upper end of the cylinder both by the accumulator Q and by displacement of fluid from the lower end of the cylinder during the downstroke; and by blocking return flow from the lower end of the cylinder to the main reservoir, an isolated or closed circuit is formed throughout the working stroke. Moreover, the ram cylinder assembly will act much in the manner of a displacement pump under the combined force of fluid applied from the accumulator and fluid displacement circuit to force the ram and attached tool through the power down stroke. This has the important advantage of permitting the ram accumulator to be pressurized or charged to a capacity well beyond that of the main pump, and to supplement the fluid pressure from the ram accumulator with the fluid displaced from the lower end of the cylinder, both to generate a greater working force behind the piston and also to remove from the system return line and main reservoir any shock otherwise in troduced by the sudden displacement-of fluid from the lower end of the cylinder.

in the remote control valve assembly, essentially the power down stroke is initiated by pressurizingline K, from the selector valve K to open the pilot check valve B and pressurizing line 1 leading from the selector valve J to open the pilot check valve C for communication between the accumulator Q and fluid displacement circuit with the upper and lower ends of the ram cylinder assembly T. Simultaneously, the control valve A is shifted to a position blocking return flow through the line M2. In addition, a check valve 124 in the lift line 110 serves to block return flow through this line from the fluid displacement circuit.

The lift or return stroke of the piston 85 in the power cylinder is initiated by allowing the pilot check valves B and C to close when the main stroke control valve A is shifted to a position which will establish fluid communication between the supply line 108 and lift line lltl, return line 112 exhausting fluid from the upper end of the cylinder through the system return 102. Since pilot check valves B and C are closed, fluid applied under pressure through the line lltl will flow in a reverse direction in succession through lines 116, 115, RM and the feed tube 52 to the lower end of the cylinder in order to impart lift pressure to the piston. Of particular note is that under reverse flow of fluid through the pressure booster N to the lower end of the cylinder, fluid is initially supplied under increased pressure by the pressure booster to effect rapid initial acceleration of the piston whereby to overcome any initial resistance to upward movement of the tool, such as for instance, if the tool has become lodged or stuck. At the same time, fluid displaced through the upper end of the cylinder is exhausted through the return line M2 to the system return l02.

STROKE LENGTH CONTROL The stroke length of the ram is regulated through the trip cylinder assembly U. As shown in FIGS. 1 and 2, the trip cylinder assembly is arranged in closely spaced, parallel relation to the ram cylinder and includes a rocker arm shaft which is slidable in the through-bore 65 on the housing 54, and pivotally secured at its upper end to one end of a rocker arm 132 on the manifold 47; and the lower end of the shaft is attached to the top of a single acting cylinder 1%. A cylinder rod 137 projects downwardly through the lower end of the cylinder and in a conventional manner may be frictionally held by suitable packing in the lower end, not shown, so that its extent of downward projection in relation to the cylinder is determined by the volume of fluid supplied through pressurereturn line 138 to the upper end of the cylinder as controlled by the stroke length valve E.

The stroke length valve E is represented as a three-way closed center, center hold position valve and includes a suitable control lever 140 for actuation of a valve spool 42 against centering spring 143. Line 144, from the main supply line 108, communicates through orifice 145 with inlet port 146; and outlet port 147 communicates with the pressure-return line 138, the latter passing through an overtravel accumulator P to the top of trip cylinder 134 as described. By shifting the valve spool to the right, as viewed in FIG. 5, from its center closed position, communication is established between the line 144 and pressure line 138 to apply fluid under pressure to the trip cylinder 134 thereby forcing the trip cylinder rod 137 downwardly through the cylinder to set it at the desired position; or by shifting the valve spool to the left, the inlet port 146 is blocked and communication established from the outlet port 147 to the exhaust port 152. A relief valve including valve element 156 opposite to the inlet and outlet ports, the relief valve being set to open below the precharge pressure of the overtravel accumulator P in order to prevent excessive charging of the accumulator above a predetermined pressure level. In turn, the orifice 145 in the line 144 primarily serves to restrict fluid flow and consequent speed of movement of the cylinder rod 137 through the cylinder 134 when lowered to the desired position. The trip cylinder rod 137 is engaged by the lower end of the ram during the lift stroke to force the rocker arm shaft 130 upwardly to pivot the rocker arm 132 and briefly, through rocker arm shaft 158, to shift the pilot valve F into position in preparation for the next working or down stroke. To prevent damage to the rocker arm linkage due to over travel of the ram piston 85, the trip cylinder rod 137 is allowed to continue upwardly through the trip cylinder, after the rocker arm shaft 130 has reached its limit of movement, by permitting fluid to escape from the trip cylinder 134 into the overtravel accumulator P. Subsequently, when the ram piston is reversed in movement for the working stroke, the cylinder rod 137 is released by the lower end of the ram thus permitting fluid return through the upper end of the cylinder 134 from the overtravel accumulator P, and forcing the cylinder rod 137 to its original extended position as initially set by the stroke length control valve E. Essentially, the trip cylinder is single acting so that the cylinder rod 137 is positioned in the cylinder according to the volume and pressure of fluid acting across its top surface. Thus, to lower the cylinder rod, the valve E is actuated to supply fluid under pressure to the trip cylinder, as described; to raise the cylinder rod, the valve E is shifted to withdraw fluid from the trip cylinder, and at the same time the ram is lifted to engage the cylinder rod and advance it upwardly to the desired setting.

FLOW SENSOR ASSEMBLY AND AUTOMATIC PILOT CONTROL In general, the flow sensor assembly D operates when the ram piston 85 has reached the end of its working or return stroke to determine the direction of fluid flow through the fluid displacement circuit to and from the lower end of the power cylinder 40; and in cooperation with the automatic pilot control valve F to reverse the stroke of the ram piston during automatic cycling of the ram. For this purpose, the flow sensor includes an outer casing 190 with a cover 191 at one end and upper and lower ports 192 and 193 communicating with a central chamber 194 in the casing. Disposed for axial movement through the casing is a valve spool rod 196 which forms an extension of the rocker arm shaft 158, and an outer spool in the form of a sleeve 198 is disposed in spaced outer concentric relation to the rod with an internal spring 199 disposed between a pair of axially spaced bushings 200 and 201 on the valve rod; keepers 202 at opposite ends of the bushings serve to center the spool over the end bushings and internal spring. in addition, the spool sleeve 198 has an orifice 203 and an external peripheral shoulder or land 204; and when the spool is in centered relation external shoulder 204 is aligned with an internal shoulder or land 206 in the wall of the casing to form a seal between the ports 192 and 193, with the exception ofa bleed orifice 207 in the wall of the casing. it will be seen that fluid flow from the line through port 192 will act downwardly on the spool sleeve 198, and under pressure will cause axial movement of the sleeve and upper bushing against the internal spring, causing the spring to compress against the lower bushing and the shoulder 204 to be forced away from the internal shoulder 206 to open the chamber for communication between the ports 192 and 193. Conversely, flow from the opposite line 116 through the port 193 will tend to force the spool sleeve 198 upwardly in the same manner to establish communication between ports but in the opposite direction. The orifices in the shoulder 206 and the spool sleeve 198 are designed merely to maintain balanced pressure conditions within the flow sensor assembly when the spool sleeve is centered.

From the flow sensor casing, the valve rod 196 continues into the automatic pilot control valve F, the valve F having a casing 210 formed as an axial extension of the flow sensor casing with coaxially aligned central chamber 212 for movement of the valve rod 196 therethrough. In turn, the lower portion of the valve rod includes axially spaced spool portions 213, 214 and 215 in the valve F and terminates in a lower end 216 provided with a lock nut 217 abutting against a return spring 218, the latter being positioned within an end cap 220 at the lower end of the valve casing 210. The return spring 218 is mounted on a centering pin or limit stop 222 and is biased to urge the valve rod upwardly to a raised position as illustrated in FIG. 6.

Communicating with the central chamber in the valve body 210 are a series of pilot control lines including a pressure supply line W from the power limit valve W, control lines F and F to the automatic-manual" selector valve and exhaust line F discharging to the system return. When the valve rod is in its raised position under the urging ofthe return spring 218, the line W, communicates with control line F,, and control line F discharges through exhaust line F When however the rod is actuated downwardly, as by tripping the rocker arm and rocker arm shaft 158, the rod is moved to a position to establish communication from pressure line W to pilot control line F and F, communicates with exhaust line F In shifting the valve rod 196, it will be noted that the flow sensor spool sleeve 198 will follow its movement and also be movable independently in response to fluid flow through the fluid displacement circuit. For example, in the raised position the spool sleeve is disposed to move upwardly, in response to fluid under pressure through the lower port 193, away from the shoulder 204, to permit continued fluid flow to the lower end of the ram cylinder during the lift stroke; and when the rocker arm is tripped and the valve rod lowered at the end of the lift stroke the spool sleeve will be urged in the opposite direction by the rod 196, against fluid pressure in preparation for the next downstroke. In the latter position, the spool sleeve will open the chamber in response to fluid flow through port 192 from the lower end of the ram cylinder during the downstroke so as to hold the pilot valve rod in position throughout the downstroke. At the end of the downstroke in the absence of fluid under pressure flowing into port 192 from the lower end of the ram cylinder, the return spring 218 will return the valve rod 196 and spool sleeve 193 to the raised position for the next stroke or cycle.

REMOTE CONTROL VALVE ASSEMBLY Reference is made again to FIG. 5 for a more detailed explanation of the main hydraulic system and remote control valve assembly. Although not shown, all hand-actuated controls for operating the hammer mechanism are preferable in a centralized location accessible to a single operator; and to correlate actuation of the control valves with operation of the hammer, all stroke control signals are applied through the main stroke control valve A, whether for manual control or automatic cycling of the hammer mechanism.

More specifically, it will be seen that the valve A is positioned between the supply line 108 and the lift and return lines 3 .10 and 112 respectively to and from the ram cylinder control circuit, and also controls actuation, through the valve K, of the power limit valve W in the accumulator circuit. Thus, for the lift stroke, the valve A is shifted to the right to establish a circuit from the supply line 108 through the lift line M0 to the lower end of the ram cylinder and simultaneously will operate, through valve K, to open the power limit valve thereby permitting charging of the ram accumulator'by the higher pressure system accumulator throughout the lift stroke. On the downstroke, the stroke control valve A is shifted to the left in the relation shown in FIG. 5 and functions to block flow of fluid to and from the lift and return lines 110 and 112, respectively, as well as to permit return of the power limit valve to a closed position, thus blocking return' flow from the ram cylinder and cooperating to isolate, the ram cylinder circuit throughout its downstroke.

in the preferred form, valve A consists of a valve body 260 having a supply port 262 from line 108 together with lift line port 263 and return line port 264, all in communication with a central valve chamber 265. Slidable in the chamber is a valve cycle spool 266 having a reduced end portion 268 with servo piston 269 projecting from the reduced end portion through a bore 270 in the control valve K. A port 272 at the end of the bore is provided for connection line 273 from the main supply line 108. Also, a spool shift spring 274 is disposed on the reduced end portion between the spool proper and a stop element 275 at the end of the valve A.

The opposite end of the main valve spool 266 includes a servo piston 276 having an end port 277 for connection of plot control line J from the automatic-manual selector valve J. Es sentially, pressurizing the pilot control line J will force the servo piston to the right, overcoming the force of the shift spring 274 and the fluid acting against the piston 269, to establish communication between the supply port 262 and lift line port 263, as well as between the return line port 264 and an exhaust port 275 to the system return. When pressure is removed from the pilot control line J for example, to signal the end of the lift stroke, the shift spring 274 and piston 269 will return the valve spool to a position blocking flow between the return line port 264 and exhaust .port 275. In this way, the servo piston 269 in cooperation with the shift spring 275 is effective to rapidly shift the main control spool to a position blocking the supply port 262 and return port 263 prior to initiation of the downstroke, thereby insuring that the control valve A is closed before the pilot check valves B and C are opened at the start of the downstroke.

in order to control the speed of opening movement of the valve spool 266, for the lift stroke an orifice check valve 280 shown in FIG. 7 is positioned in the valve body 260 opposite the reduced end portion 263. The orifice check valve is provided with a valve body 202 disposed across an exhaust port with an orifice 204 in the body communicating between the exhaust port 275 and the chamber area 285 surrounding the reduced end when fluid pressure is applied through line J against the servo piston 276 to initiate the lift stroke, the check valve closes and fluid trapped in'chamber 285 must bleed thru the orifice 284 in order to permit the spool 266 to shift. Thus, the check valve will resist spool movement to a certain extent and prevent sudden movement or slamming of the valve spool 266 in opening the supply port 262 at the beginning of the lift stroke.

As previously stated, the ram may be actuated through its power down stroke by opening both valves B and C, or may merely be actuated through a gravity down stroke by opening only the check valve C in the displacement circuit. This selection is made by actuation of the selector valve K which has a valve spool 290 movable through chamber 292 on the side of the stop element 275 opposite the main spool for control valve Hil A. Communicating with the chamber 292 is pilot control line J, from the selector valve .1 and control line K, leading to pilot check valve B. In addition, a pilot control line K leads from a port 204, shown dotted, in the valve K to pilot limit valve W; and the line K is selectively pressurized through bore 295 extending from the lift line port 263 into the pilot control chamber 292 adjacent to the port 294. The spool 290 is shifted, to selectively open and close the lines .l K, and K by means of a manual push-pull knob 296; and by inward displacement of the spool to power down position the control surfaces on the spool are aligned to establish a circuit from line J, to line K, for opening pilot check valve B to permit fluid flow from the ram accumulator Q to the ram cylinder. Moreover when the main spool 266 is shifted for the lift stroke, the lift line 110 being open will deliver fluid through the bore 295 and port 263 to pressurize control line leading to power limit valve W to open same and permit charging of the ram accumulator for the next power down stroke.

in order to set the valve K for a gravity down" stroke, the selector valve spool 290 is displaced outwardly by the control knob 296 to interrupt fluid flow between the control lines J and K, while permitting the line K to discharge through bore 295 past the spool 266 to exhaust port 275. In this way, the pilot check valve B remains closed during the down stroke, as does the power limit valve W to prevent charging of the ram accumulator during the lift stroke; and only the pilot check valve C is opened by control line J, to form a circuit for flow from the lower to the upper end of the ram cylinder and allow the ram piston to fall under the weight of the ram 10 and tool 11.

Now considering in more detail the construction and arrangement of the power limit valve W as shown in FIG. 5 and in more detail in FIG. 9, it is responsive to pressurizing of the control line K, from the selector valve K to open the line 107 between the system accumulator V and ram accumulator Q, and will permit charging to a predetermined level by means of a manual control setting on the valve. Referring to FIG. 9, the valve has a valve body 300 with a main valve chamber 301 for a valve spool 302 positioned therein. Communicating with the valve chamber is a post 304 for pressure line W, leading to the pilot valve F, and an inlet port 305 and outlet port 306 provide pressure connections for line 107 extending from the system accumulator V to the ram accumulator O. Preferably, the inlet port 305 is in the form of a broad open port extending upwardly through the thickness of the valve body and the central chamber 301 into the bore 304. Accordingly, the inlet port 305 is in constant communication with the pressure port 304 for line W,, whereas communication between inlet port 305 and outlet port 306 is of course controlled by movement of the spool 302 in the valve chamber. Initial setting of the spool 302 in relation to the ports is controlled by a screw adjustment member 307 including a threaded stern 300 disposed in a threaded end portion 309 for projection into the chamber 301 from one end of the valve, and the stem is provided with a return spring 316 extending through a bore 318 in one end of the spool. A piston chamber 310 is disposed at the opposite end of the valve body and in which is positioned a servo piston 312 with port 313 communicating with the piston chamber from the control line K At the beginning of the lift stroke, when the control line K from the valve K is pressurized to apply fluid under pressure to the port 313, the servo piston 312 is displaced to shift the spool through the valve chamber 301 against the end of the stem 300 to open the outlet port a predetermined extent, depending upon the setting of the stern 308 in the chamber. When fluid is exhausted through the pilot control line K the return spring will return the spool 302 to its initial setting blocking flow between the inlet and outlet ports, and which action will occur at the end of the lift stroke.

It will be seen therefore that the ram accumulator Q is charged a predetermined amount dependent upon the screw adjustment setting of the power limit valve W together with the length of stroke setting by valve E, since the latter will determine duration of charging and the volume of fluid that ill.

will pass from the system accumulator V to the ram accumulator Q during the lift stroke. Again, the pilot control line K is exhausted at the end of the lift stroke when the stroke control valve A returns to its position blocking the port 262 while relieving pressure from the line K, to the exhaust port 275.

In order to control lift stroke speed and balance, a conventional throttle valve H is disposed in the supply line 108 to the main control valve A and merely functions to throttle flow by means of a manual adjustment knob 320. Again, in somewhat the same manner as the power limit valve W, by adjusting the knob 320 in desired relation within the valve body, a spool, not shown, is positioned to control capacity of flow from an inlet port 323 through outlet port 324. Therefore, the valve l-l may be closely controlled by the operator to regulate the rate of fluid flow from the pumps to the lower end of the ram cylinder, and consequently regulate speed of travel in cooperation with the pressure booster N of the ram piston through its lift or return stroke.

From the foregoing description, it will be noted that by transmitting the appropriate fluid control signals to the valve A and to the pilot check valves B and C the hammer mechanism can be operated in either direction or continuously operated through one or more complete cycles. In accordance with the present invention, the en circuit is set either for manual or automatic operation by manual-automatic selector valve J. In FIG. 5, the valve J is represented as a two position double selector valve including a valve spool 330 and a manual control knob 332 to shift the spool 330 either to a manual position establishing communication from manual control lines M, and M to outlet lines J, and 1,, respectively; or to an automatic position forming a similar circuit from automatic control lines F, and F to the lines J, and 3,, respectively. In other words, line J, may be pressurized either by control line F, or M,, and line J may be pressurized either by control line F or M depending upon whether the valve J is set at its automatic or manual position.

The control lines M, and M lead from a manual stroke control valve Y, suitably being of the type referred to as a three position, four-way, closed center, cylinder float position valve. in construction, the valve is shown having a manual control lever 334 to shift valve spool 335 in either direction from its center hold position to control the introduction of fluid under pressure from line 336 to line M, or M In the center hold position, line M, and M are discharged through exhaust ports 338 to the system return, and the supply line 336 from the main supply line 108 is blocked. Assuming that the selector valve J is in the manual position as described, then by shifting the manual valve spool 335 to the right, or to the down position, a circuit is established from supply line 336 to control line M, and, through valve J, to control line J, leading to line J and valve K; and at the same time line M discharges fluid from line J through an exhaust port 338. By shifting the manual spool 335 to the left, or to its lift position, a circuit is established from supply line 336 to control line M and, through valve J, to servo control line J for the valve A, while at the same time exhausting control line M, for fluid return from the line J, through the exhaust port 338. When the manual control lever 334 is released, a centering spring 339 at one end of the spool 335 automatically returns the spool to the center hold position exhausting both control lines M, and M while permitting the pilot check valves B and C to close thereby holding the ram piston in position.

When the selector valve J is shifted to the automatic position, alternate pressurizing of control lines F, and F automatically in response to movement of the flow sensor assembly D and the pilot valve takes the place of selective shifting of the valve to pressurize lines M, and M as described. Accordingly, it will be seen that at the beginning of the lift stroke the flow sensor assembly D is in its raised position so that fluid flowing through lift line lit) from the control valve A passes through the lower port against the flow sensor spool sleeve 198 to urge it upwardly away from the internal shoulder 206 for flow through the pressure booster to the lower end of the ram cylinder in order to raise the ram piston through the ram cylinder.

As the ram approaches its upper limit travel, depending upon the setting of the trip cylinder U, the lower end of the ram will engage the trip cylinder rod causing it to move upwardly and pivot the rocker arm shaft 158 and attached valve rod 196 downwardly. Downward movement of the rod will overcome fluid pressure acting against the spool sleeve 198 and, in cooperation with the internal spring 199, force the spool sleeve 198 downwardly to return to closed relation against the internal shoulder, thereby interrupting fluid flow to the lower end of the ram cylinder. Simultaneously the lower spool assembly on the valve rod 196 is shifted to a position establishing communication between pressure line W, and pilot control line F, thereby pressurizing the control line J, through the selector valve J to open one or both pilot check valves B and C, while exhausting line J through line F to the exhaust port line F Of course, both valve lines K, and J:, are pressurized in response to pressurizing pilot control line F,, assuming that the valve K is in the power down" position, to initiate the down stroke. Through the downstroke, the flow sensor assembly valve rod 196 is held down, since fluid displaced from the lower end of the ram cylinder into the flow sensor assembly D will act against the upper end of the spool sleeve 198 in passing through the assembly D to the upper end of the ram cylinder.

Completion of the downstroke is signaled by a loss in pressure when the ram and attached tool strike the work surface and stop moving, or when the ram piston passes the inlet port 69 and moves against the lower end of the ram cylinder under uniformly decelerated motion. Under a loss in fluid pressure the spool sleeve 138 will immediately return upwardly into sealed relation with the internal shoulder, thereby selectively blocking the fluid circuit in a direction from the lower to the upper end of the ram cylinder; and the return spring 218 will cause the valve rod and spool in the pilot control valve F to shift to a position establishing circuit flow from the line W, to line F while discharging line F, through port F,,, as a result of which the main control valve A is shifted to the lift stroke position for fluid flow through lift line 110 to repeat the cycle. It is important to note in this connection that the spool sleeve 198 in the flow sensor assembly D will operate independently of the automatic pilot control valve F to sense both direction and pressure of fluid flow through the displacement circuit once it is positioned by mechanical actuation of the valve rod 196, either in response to the return spring 199 at the end of the downstroke or in response to pivoting of the rocker arm 132 upon completion of the lift stroke.

The preferred form of hammer mechanism, under selective control of the ram cylinder circuit and remote control valve circuitry devised, offers a number of distinct advantages in use, and especially as adapted for use in portable or mobile hammer units.

Summarizing many of the features inherent in the operation ofthe hammer mechanism, when the selector valve J is shifted to the manual" position, the valve A can be actuated by manual control valve Y with the valve K disposed either in the power down" or gravity drop" position as described. Shifting the valve Y in one direction will cause the piston to move downward, or shifting the valve in the opposite direction will cause the piston to move upward the desired distance. When the valve control lever 334 is released, the valve spool 335 returns to the center hold position causing the ram piston to stop and hold in position. For the automatic strike cycle, the selector valve J is placed in the "automatic" position so that fluid flow from pilot control valve F alternately through pilot control lines F, and F actuates the stroke control valve A, again to force the ram piston up and down until stopped by returning the selector J to the manual position. Normally, the piston 85 is reversed from its downward stroke when the impact tool strikes an object and is stopped or, in the event of overtravel past the port 69, when it reaches the lower end limit of travel within the power cylinder, and in either case the resultant loss in pressure through the fluid displacement circuit to the flow sensor D will permit the valve rod 1% to be raised by the return spring to transmit a fluid control signal through line F to the stroke control valve A to initiate the lift or return stroke. Again, fluid pressure from the valve A through lift line llll in the reverse direction through the fluid displacement circuit to the bottom of the power cylinder will force the ram piston upwardly until the lower end of the hammer weight contacts or engages the trip cylinder rod 137. The rod H37 will actuate the valve rod 1% downwardly through the flow sensor assembly D thereby blocking con tinued fluid flow to the lower end of the power cylinder and also reversing the pilot control valve F to transmit a fluid control signal through line F, to the control valve A and selector valve K. Assuming that the selector valve K is in the power down position, fluid control signals are then transmitted to apply opening pressure to both pilot check valves B and C for fluid flow through the cylinder head to the upper end of the power cylinder both from the accumulator Q and by returning fluid displaced from the bottom of the cylinder through the fluid displacement circuit to the top of the cylinder. The cycle is repeated when the piston has reached the end of its downstroke or is stopped by an external force, and of course the cycle will repeat itself for as long as the selector valve l remains in the automatic position and likewise if the selector valve K were in the gravity drop position as this would effect only the opening and closing of the pilot check valve'B for the accumulator Q. Moreover, the lift stroke pressure booster N will effect an initial pressure increase at the beginning of the lift stroke whether in the manual or automatic position, or in the power down or gravity drop position.

Length of stroke, speed, powerand balance may be independently regulated both during automatic and manual operation, and are under the direct control of the operator at all times; yet the ram cylinder circuit-is self-regulating with the necessary built-in safety features to prevent damage to the hammer mechanism, for instance, in' the event that the hammer tool 11 is suddenly stopped short of its full stroke or if for any reason it should overtravel in either direction beyond its intended stroke. It is further possible to develop considerably more power in the ram cylinder circuit due to the manner in which the ram piston is displaced through the down stroke while isolating the main system from the ram cylinder circuit. As an illustration, utilizing a pump capable of developing 2200 pounds per square inch pressure with gallons per minute flow, it has been possible to generate an impact force on the order of 1600 foot pounds and capable of delivering 40 to 4-5 blows per minute. Of course the increased power and velocity of stroke permits use of a relatively lightweight ram or hammer weight as described in our hereinbefore referred to copending application, and in general the entire mechanism is thus highly economical, fully protected with regard to safety of both the operator and machine and completely flexible so as to enable its efficient use in a variety of operations, such as for example, concrete breaking, scoring and cutting, tamping or earth compaction work as well as for asphalt cutting and paving operations. For instance, in asphalt cutting operations where the tool would have a tendency to get stuck, the automatic pressure boost at the beginning of the lift stroke will supply ample force to rapidly free the tool; and, again, rapid acceleration throughout the downstroke will generate a greater force over arelatively short distance of stroke.

it is therefore to be understood that while the form of apparatus and control circuitry herein described constitutes a preferred embodiment of the present invention, various modifications and changes may be resorted to without departing from the spirit of the present invention.

We claim:

ll. In a hydraulically actuated hammer unit having an impact tool mounted for reciprocation through a working and return stroke, the combination of a double acting cylinder assembly comprising a cylinder body providing a chamber, a first port at one end of the chamber, a pair of ports arranged in axially spaced relation to one another for the purpose of supplying fluid to and receiving fluid from the opposite end of said chamber, a piston reciprocal within the chamber through a normal operating range short of the opposite ends of said chamber to impart a working and return stroke to said impact tool, fluid supply means to supply fluid under pressure through said first port to the one end of said chamber to operate said piston through a working stroke whereby fluid ahead of said piston is displaced through one of said pair of ports, pressure control means defined by a series of axially spaced grooves arranged between said piston and chamber, the spacing between grooves being such that the grooves are operable upon said piston moving beyond its normal range past said one port to impart uniformly decelerated motion to said piston under continued movement toward the opposite end of the chamber, and means to supply fluid under pressure through the other of said pair of ports to initially displace said piston for movement through its return stroke toward the one end of said chamber.

2. In a hydraulically actuated hammer unit according to claim 1, in which said cylinder assembly further includes check valve means associated with said other port to selective admit fluid into the opposite end of said chamber, and an error relief valve associated with said one port.

3. In a hydraulically actuated hammer unit according to claim 2, in which said cylinder assembly includes control means between said piston and the one end of said cylinder operable upon overtravel of said piston through its return stroke to uniformly and rapidly decelerate the speed of travel of said piston in approaching the one end 'of said cylinder.

4. In a hydraulically actuated hammer unit according to claim 2, in which an external fluid displacement circuit is provided to conduct fluid displaced from the opposite end of the chamber by said piston during its working stroke to the one end of the chamber whereby to supplement the flow of fluid from said pressure supply means.

5. In a hydraulically actuated hammer unit having an impact tool mounted for reciprocation through a working and return stroke, the combination of a double acting cylinder assembly comprising a cylinder body providing a main elongated chamber, a first port at one end of the chamber including a bore of reduced size at the one end of the chamber in coaxial alignment with the chamber, a pair of inner and outer ports arranged in axially spaced relation to one another at the opposite end of the chamber, a piston rod assembly including a piston rod movable through and projecting outwardly from the opposite end of the chamber for attachment to said impact tool and a differential piston reciprocal within said chamber to impart a working and return stroke to said impact tool, fluid supply means to supply fluid under pressure to said first port and to said pair of ports to operate said piston through the working stroke whereby fluid between said piston and the opposite end of said chamber is normally displaced through said inner port, first pressure control means for said piston being operable upon said piston moving through its working stroke past said inner port to impart uniformly decelerated motion to said piston by restricted'passage of fluid past the piston into said inner port, fluid return means including a return line to discharge fluid from the one end of said cylinder and a pressure line to supply fluid under pressure through said outer port when fluid is discharged from the one end of said cylinder to initially displace said piston for movement through its return stroke toward the one end of said chamber and to supply fluid through said inner port when said piston has passed said inner port to complete the return stroke, and second pressure control means operable upon overtravel of said piston through its return stroke to uniformly and rapidly decelerate the speed of travel of said piston in approaching the one end of said cylinder, said second pressure control means being definedby a reduced end portion on said piston movable into the bore at the one end of said chamber and including a series if spaced peripheral grooves thereon which upon movement into the bore will impose progressively increasing resistance to passage of fluid through the bore into said first port.

6. In a hydraulically actuated hammer unit having an impact tool mounted for reciprocation through a working and return stroke, the combination of a double acting cylinder assembly comprising a cylinder body providing an elongated cylindrical chamber, a first port at one end of the chamber, a pair of inner and outer ports arranged in axially spaced relation to one another at the opposite end of said chamber, a cylindrical piston reciprocal within the chamber to impart a working and return stroke to said impact tool, fluid supply means to supply fluid under pressure to opposite ends of said chamber to actuate said piston through a working stroke whereby fluid between said piston and the opposite end of said chamber is normally displaced through said inner port with a series of axially spaced grooves being arranged between said piston and the chamber wall between said inner and outer ports being effective upon said piston moving during its working stroke past said inner port to impart uniformly decelerated motion to said piston by restricting the passage of fluid past said piston into said inner port, said axially spaced grooves arranged in the external surface of said piston, and the spacing between grooves being progressively reduced toward said inner port to impose an increasing resistance to discharge of fluid into said inner port in direct relation to decelerated movement of said piston past said inner port, and check valve means being disposed in said outer port to selectively admit fluid under pressure into the opposite end of the chamber to displace said piston away from the opposite end for movement through its return stroke.

8. A hydraulically operated hammer mechanism according to claim 7, said piston being movable through a normal operating range short of the opposite ends of the chamber, and pressure control means associated with said piston being operative to impart a uniformly decelerated motion to said piston in response to piston travel beyond the normal operating range in either direction of movement.

7. A hydraulically operated hammer mechanism comprising a guide frame assembly including vertical guideways, a hammer weight having an impact tool suspended at its lower end with said hammer weight mounted for slidable, reciprocal movement along said vertical guideways through a power down stroke and a lift return stroke, a cylinder assembly sup ported on said guide frame assembly comprising a cylinder body providing an elongated vertical chamber, means for supplying fluid to and receiving fluid from opposite ends of the chamber, a piston rod assembly including a piston rod projecting downwardly through the lower end of the chamber and a differential piston thereon being movable in sealed relation through the chamber, cylinder supporting means to mount the upper end of said cylinder body in swiveled relation to said guide frame assembly for vertical downward suspension of said cylinder assembly therefrom, and supporting means for attaching said hammer weight in swiveled relation to the lower end of said piston rod to provide for vertical sliding movement of said hammer weight along said guideways in response to actuation of said piston through the chamber.

8. A hydraulically operated hammer mechanism according to claim 7, said piston being movable through a normal operating range short of the opposite ends of the chamber, and pressure control means associated with said piston being operative to impart a uniformly decelerated motion to said piston in response to piston travel beyond the normal operating range in either direction of movement.

9. A hydraulically operated hammer mechanism according to claim 7, in which said cylinder assembly is characterized by including a cylinder head with lateral fluid supply port therein communicating with the upper end of the chamber, fluid conducting means including laterally extending fluid supply means at the lower end of the chamber, and a back up member extending laterally between said cylinder and said guide frame assembly to counteract side loading effects of fluid applied under pressure through said lateral fluid supply port and lateral fluid supply means.

10. A hydraulically operated hammer mechanism according to claim 9, in which said fluid conductin means includes a reinforcing sleeve in surrounding relation 0 the lower end of said cylinder, and said laterally extending fluid supply means is defined by axially spaced upper and lower fluid supply ports communicating with the lower end of the chamber, said fluid supply ports at the upper and lower ends of said cylinder being aligned such that fluid applied under pressure therethrough will develop loading moments in a corresponding direction about said cylinder supporting means.

11. a hydraulically operated hammer mechanism comprising: a guide frame assembly including vertical guideways, a hammer weight having an impact tool suspended at its lower end with said hammer weight mounted for slidable and reciprocal movement along said vertical guideways through a power down stroke and lift return stroke; a cylinder assembly comprising a power cylinder body including an upper end portion mounted in swiveled relation to said guide frame assembly and including a central elongated chamber therein; a cylinder head at the upper end of said cylinder body having a fluid pressure port with an entrance bore of reduced size extending in coaxial relation into the upper end of the chamber; a reinforcing sleeve disposed in surrounding relation to the lower end of said cylinder body and being provided with an upper port communicating with the chamber in spaced relation above the lower end of the chamber, and with a bore of reduced size defining a coaxial extension from the lower end of the chamber, a feed tube communicating through a common groove in said reinforcing sleeve with said upper and lower ports including check valve means in the groove adjacent said lower port and relief valve means in communication through a separate groove with said lower port; a piston rod assembly including a piston rod projecting downwardly through the lower bore for attachment of said hammer weight to the lower projecting end of said rod, and an elongated differential displacement piston movable in sealed relation through the chamber with a series of axially spaced peripheral grooves on the surface of said piston being spaced to decelerate said piston in moving past said upper port toward the lower end of the chamber on the downstroke and an upper reduced end portion on said piston with a series of spaced peripheral grooves thereon being adapted to move through the cylinder head bore in approaching the upper end limit of travel through the chamber on the return stroke.

12. A hydraulically operated hammer mechanism according to claim 11, in which said hammer weight is characterized by being of hollow heavy walled configuration with a closed lower end portion for attachment of said impact tool, and the lower end of said piston rod projecting downwardly through said hammer weight for attachment in swiveled relation to the lower closed end thereof. 

1. In a hydraulically actuated hammer unit having an impact tool mounted for reciprocation through a working and return stroke, the combination of a double acting cylinder assembly comprising a cylinder body providing a chamber, a first port at one end of the chamber, a pair of ports arranged in axially spaced relation to one another for the purpose of supplying fluid to and receiving fluid from the opposite end of said chamber, a piston reciprocal within the chamber through a normal operating range short of the opposite ends of said chamber to impart a working and return stroke to said impact tool, fluid supply means to supply fluid under pressure through said first port to the one end of said chamber to operate said piston through a working stroke whereby fluid ahead of said piston is displaced through one of said pair of ports, pressure control means defined by a series of axially spaced grooves arranged between said piston and chamber, the spacing between grooves being such that the grooves are operable upon said piston moving beyond its normal range past said one port to impart uniformly decelerated motion to said piston under continued movement toward the opposite end of the chamber, and means to supply fluid under pressure through the other of said pair of ports to initially displace said piston for movement through its return stroke toward the one end of said chamber.
 2. In a hydraulically actuated hammer unit according to claim 1, in which said cylinder assembly further includes check valve means associated with said other port to selective admit fluid into the opposite end of said chamber, and an error relief valve associated with said one port.
 3. In a hydraulically actuated hammer unit according to claim 2, in which said cylinder assembly includes control means between said piston and the one end of said cylinder operable upon overtravel of said piston through its return stroke to uniformly and rapidly decelerate the speed of travel of said piston in approaching the one end of said cylinder.
 4. In a hydraulically actuated hammer unit according to claim 2, in which an external fluid displacement circuit is provided to conduct fluid displaced from the opposite end of the chamber by said piston during its working stroke to the one end of the chamber whereby to supplement the flow of fluid from said pressure supply means.
 5. In a hydraulically actuaTed hammer unit having an impact tool mounted for reciprocation through a working and return stroke, the combination of a double acting cylinder assembly comprising a cylinder body providing a main elongated chamber, a first port at one end of the chamber including a bore of reduced size at the one end of the chamber in coaxial alignment with the chamber, a pair of inner and outer ports arranged in axially spaced relation to one another at the opposite end of the chamber, a piston rod assembly including a piston rod movable through and projecting outwardly from the opposite end of the chamber for attachment to said impact tool and a differential piston reciprocal within said chamber to impart a working and return stroke to said impact tool, fluid supply means to supply fluid under pressure to said first port and to said pair of ports to operate said piston through the working stroke whereby fluid between said piston and the opposite end of said chamber is normally displaced through said inner port, first pressure control means for said piston being operable upon said piston moving through its working stroke past said inner port to impart uniformly decelerated motion to said piston by restricted passage of fluid past the piston into said inner port, fluid return means including a return line to discharge fluid from the one end of said cylinder and a pressure line to supply fluid under pressure through said outer port when fluid is discharged from the one end of said cylinder to initially displace said piston for movement through its return stroke toward the one end of said chamber and to supply fluid through said inner port when said piston has passed said inner port to complete the return stroke, and second pressure control means operable upon overtravel of said piston through its return stroke to uniformly and rapidly decelerate the speed of travel of said piston in approaching the one end of said cylinder, said second pressure control means being defined by a reduced end portion on said piston movable into the bore at the one end of said chamber and including a series if spaced peripheral grooves thereon which upon movement into the bore will impose progressively increasing resistance to passage of fluid through the bore into said first port.
 6. In a hydraulically actuated hammer unit having an impact tool mounted for reciprocation through a working and return stroke, the combination of a double acting cylinder assembly comprising a cylinder body providing an elongated cylindrical chamber, a first port at one end of the chamber, a pair of inner and outer ports arranged in axially spaced relation to one another at the opposite end of said chamber, a cylindrical piston reciprocal within the chamber to impart a working and return stroke to said impact tool, fluid supply means to supply fluid under pressure to opposite ends of said chamber to actuate said piston through a working stroke whereby fluid between said piston and the opposite end of said chamber is normally displaced through said inner port with a series of axially spaced grooves being arranged between said piston and the chamber wall between said inner and outer ports being effective upon said piston moving during its working stroke past said inner port to impart uniformly decelerated motion to said piston by restricting the passage of fluid past said piston into said inner port, said axially spaced grooves arranged in the external surface of said piston, and the spacing between grooves being progressively reduced toward said inner port to impose an increasing resistance to discharge of fluid into said inner port in direct relation to decelerated movement of said piston past said inner port, and check valve means being disposed in said outer port to selectively admit fluid under pressure into the opposite end of the chamber to displace said piston away from the opposite end for movement through its return stroke.
 7. A hydraulically operated hammer mechanism comprising a guide frame assembly including vertical guideways, a hammer weight having an impact tool suspended at its lower end with said hammer weight mounted for slidable, reciprocal movement along said vertical guideways through a power down stroke and a lift return stroke, a cylinder assembly supported on said guide frame assembly comprising a cylinder body providing an elongated vertical chamber, means for supplying fluid to and receiving fluid from opposite ends of the chamber, a piston rod assembly including a piston rod projecting downwardly through the lower end of the chamber and a differential piston thereon being movable in sealed relation through the chamber, cylinder supporting means to mount the upper end of said cylinder body in swiveled relation to said guide frame assembly for vertical downward suspension of said cylinder assembly therefrom, and supporting means for attaching said hammer weight in swiveled relation to the lower end of said piston rod to provide for vertical sliding movement of said hammer weight along said guideways in response to actuation of said piston through the chamber.
 8. A hydraulically operated hammer mechanism according to claim 7, said piston being movabLe through a normal operating range short of the opposite ends of the chamber, and pressure control means associated with said piston being operative to impart a uniformly decelerated motion to said piston in response to piston travel beyond the normal operating range in either direction of movement.
 8. A hydraulically operated hammer mechanism according to claim 7, said piston being movable through a normal operating range short of the opposite ends of the chamber, and pressure control means associated with said piston being operative to impart a uniformly decelerated motion to said piston in response to piston travel beyond the normal operating range in either direction of movement.
 9. A hydraulically operated hammer mechanism according to claim 7, in which said cylinder assembly is characterized by including a cylinder head with lateral fluid supply port therein communicating with the upper end of the chamber, fluid conducting means including laterally extending fluid supply means at the lower end of the chamber, and a back up member extending laterally between said cylinder and said guide frame assembly to counteract side loading effects of fluid applied under pressure through said lateral fluid supply port and lateral fluid supply means.
 10. A hydraulically operated hammer mechanism according to claim 9, in which said fluid conducting means includes a reinforcing sleeve in surrounding relation to the lower end of said cylinder, and said laterally extending fluid supply means is defined by axially spaced upper and lower fluid supply ports communicating with the lower end of the chamber, said fluid supply ports at the upper and lower ends of said cylinder being aligned such that fluid applied under pressure therethrough will develop loading moments in a corresponding direction about said cylinder supporting means.
 11. a hydraulically operated hammer mechanism comprising: a guide frame assembly including vertical guideways, a hammer weight having an impact tool suspended at its lower end with said hammer weight mounted for slidable and reciprocal movement along said vertical guideways through a power down stroke and lift return stroke; a cylinder assembly comprising a power cylinder body including an upper end portion mounted in swiveled relation to said guide frame assembly and including a central elongated chamber therein; a cylinder head at the upper end of said cylinder body having a fluid pressure port with an entrance bore of reduced size extending in coaxial relation into the upper end of the chamber; a reinforcing sleeve disposed in surrounding relation to the lower end of said cylinder body and being provided with an upper port communicating with the chamber in spaced relation above the lower end of the chamber, and with a bore of reduced size defining a coaxial extension from the lower end of the cHamber, a feed tube communicating through a common groove in said reinforcing sleeve with said upper and lower ports including check valve means in the groove adjacent said lower port and relief valve means in communication through a separate groove with said lower port; a piston rod assembly including a piston rod projecting downwardly through the lower bore for attachment of said hammer weight to the lower projecting end of said rod, and an elongated differential displacement piston movable in sealed relation through the chamber with a series of axially spaced peripheral grooves on the surface of said piston being spaced to decelerate said piston in moving past said upper port toward the lower end of the chamber on the downstroke and an upper reduced end portion on said piston with a series of spaced peripheral grooves thereon being adapted to move through the cylinder head bore in approaching the upper end limit of travel through the chamber on the return stroke.
 12. A hydraulically operated hammer mechanism according to claim 11, in which said hammer weight is characterized by being of hollow heavy walled configuration with a closed lower end portion for attachment of said impact tool, and the lower end of said piston rod projecting downwardly through said hammer weight for attachment in swiveled relation to the lower closed end thereof. 